#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main() {
    char a = 0;
    scanf("%c", &a);
    if ((a <= 'Z' && a >= 'A') || (a <= 'z' && a >= 'a'))
    {
        printf("YES\n");
    }
    else
    {
        printf("NO\n");
    }
    return 0;
}